Electrical outlet with movable closure



July 18, 1950 P. E. HAMILTON 2,515,870

ELECTRICAL OUTLET WITH MOVABLE CLOSURE Filed Feb. 28, 1949 BEE-l.-

INVENTOR. PH. 10 E HqMura/v Patented July 18, 1956 UNITED STATES. PATENT OFFICE ELECTRICAL OUTLET WITH MOVABLE CLOSURE 1 Claim.

This invention relates to an electrical outlet with movable closure and more particularly to a safety outlet for the reception of plugs on extension cords.

This application is a continuation-in-part of my co-pending application Serial No. 49,268, entitled Electrical Outlet, and filed on September 14, 1948.

In the usual electrical outlet, electrical conductors connected with the source of electricity are situated at the base of recesses which are continually open when the outlet is not in use.

- The recesses are spaced for the reception of the plugs which make contact with the electrical conductors at the base of the recesses. In these conventional fittings, which most often are located slightly above floor level, dirt is free to pass into the recesses. Moreover, it is possible that hairpins and other metallic objects may be inserted in the recesses, for example, by young children and shock the child or cause a short circuit.

In order to overcome the objections to the ordinary outlets, outlets have been designed with a rotating shutter which is normally in a position to close the recesses and prevent the entrance of foreign materials. The safety outlets of this type have heretofore been rather difiicult to assemble which adds greatly to their cost of manufacture. Ordinarily, the outlets are made of relatively low cost materials and sold at a low price. Clearly, a complicated structure which is difficult to assemble cannot be commercially successful.

It is increasingly the practice to manufacture electrical appliances with a wire grounding the non-current-carrying metal parts of the appliance and a live wire to the electrical load. Appliances wired in this manner require a positive means preventing inadvertent connection of the ground wire of the appliance to the live wire of the outlets. Obviously, any advantages in safety resulting from the grounding of the appliance are more than overcome if there is a possibility of connecting the ground wire to the hot wire of the outlet.

It is, of course, necessary to construct most parts of the outlet of non-conducting materials. The materials usually employed are various plastic compositions which in most cases have low strength, as compared with metals. It is, therefore, desirable to provide a safety outlet in which the parts thereof are subjected to minimum strains.

It is an object of this invention to provide a safety electrical outlet which closes the recesses in the female electrical connection when the outlet is not in use.

Another object of this invention is to provide an electrical outlet of the safety type which may be easily manufactured and sold at a low price.

It is also an object of this invention to provide a safety electrical receptacle in which the parts are thoroughly insulated and protected to eliminate any possibility of one using the receptacle receiving a shock.

Still another object of this invention is to provide a safety outlet for use with appliances having the non-current-carrying parts grounded, in which connection of the ground Wire of the appliance with the live wire of an electrical outlet is prevented.

With these and other objects in view which will become apparent in the detailed description following, this invention resides in an electrical receptacle having electrical conductors in a base member. A shield lies over the conductors having openings in alignment with the conductors and rotatably supporting a shutter having openings normally out of register with the openings in the shield. The shutter and shield each have an opening of one size for reception of a prong of a plug which engages one conductor in the base member and an opening of a different size or shape for the reception of a prong which engages the other conductor. Means limiting the rotation of the shutter are provided allowing the openings in the shutter to move into alignment only with corresponding openings in the shield.

In the drawings:

Figure 1 is a top plan View of the completely assembled electrical outlet comprising this invention;

Figure 2 is a Vertical sectional view along section line 2-2 in Figure 1 illustrating the assembled outlet;

Figure 3 is a horizontal sectional view along the section line 3-3 in Figure 2 showing the shield on which the shutter turns;

Figure 4 is also a horizontal sectional view taken along the section line 44 in Figure 1 illustrating the position of the conductors in the outlet base of the outlet; and

Figure 5 is an exploded perspective view of the retainer shutter and shield of the outlet described herein.

For purposes of illustration, this invention is described with reference to an outlet having receptacles for plugs from two extension cords. Referring to Figure 2, a wall outlet, indicated preferable to have the conductors i2 and and their respective screws 24 different colors to 3 generally by is illustrated as installed in a casing 2, situated in a wall or floor. A bracket 3, attached to the casing 2 by means of screws 4 and to the base member 5 of the outlet by means of screws 6, supports the electrical outlet in the casing. A conventional cover plate 1 is secured over the outlet by means of a, screw 8 and completely hides the casing 2.

Referring to Figure 4 of the drawings, the base member 5 consists of a block of insulating material having recesses 9 and I! for the reception of a grounded conductor l2 and a live or hot wire connection l3. Recess'es 9 and H are separated by a, rib M, extending the full length of the base member 5.

Rib M of base member 5 has a cavity it for the reception of a post in the assembly of the outlet and sockets i5 and H, which provide bearing spaces for the hub of a shutter employed in this device, in the manner hereinafter described. As is best illus'trated'in Figure -2 of the drawings, the lower ends of sockets l5 and i! -'are grooved as at |8 and Hi for the reception of torsion springs 2| and 22. When the base member 5 is symmetrical it is desirable to drill a hole 23 in the upper surface of rib 4 to insure the proper positioning of the parts during assembly of the outlet.

Conductors i2 and I3 are provided with the usual screws 24 for the attachmentof the lead Wires to the conductors. Generally, it will be i3 facilitate the proper connection of the receptacle when it is installed. In many instances, it will be desirable to mark the outer surface of the base member 5, adjacent conductor l2, with the word ground.

Afiat shield 25 of insulating material having a central opening 25 is placed di ectly over the base member 5 with the opening 25 in alignment with cavity :5 of the base member. llhe shield 25 also has holes 2'! and 28 drilled therethrough in alignment with the sockets l5 and IT in the rib M of the basemember.

Shield 25. is provided with elongated slots 29 extending therethrough to permi'tthe insertion of the prong of a plug 'of an extension cord into contact with the electrical conductor E2 in the base member 5. Shortened slots 3! also are provided directly opposite the elongated slots 29 and permit contact with the live conductor 63 in the base member 5. The upper surface of the shield 25 is grooved at 32 and 33 by cutting away a portion of the edge of the shield. The grooves 32 and 33 provide positive. means preventing contact of the ground wire of the appliance with the conductor I3 in the manner hereinafter described.

The lower surface of the shield member in the outlet illustrated in the drawings is symmetrical and it is possible that the shield could be installed in a reversed position. To insure the proper positioning of the shield during assembly of the outlet, a pin 33, illustrated in Figure 2, is provided on the lower surface of the shield 25. Pin 30 extends into the hole 23 when the shield is properly placed on the base member 5.

Flat, disc-like shutters 34 and 35, also of an insulating material, are placed on the upper surface of the shield 25. Shutter 34 has a hub 36 extending from its lower surface into the hole 2? in the shield 25 and the socket it in the base member 5. Hub 36 serves as an axis about which the shutter rotates. Shutter 35 is similarly equipped with a hub 37, which extends through hole 28 in the shield into the socket H in the base member 5. Hubs 36 and 3'! are grooved at their lower ends for engagement with the torsion springs 2| and 22, respectively.

An elongated slot 38, having a substantially identical configuration as slot 29, in the shield 25, is provided in shutter" 3 and a similar slot 39 is provided in shutter 35. Shutter 34 is also provided with a shortened slot 4|, substantially identical in size with slot 3| in the shield 25. A similar slot 4-2 is provided in the shutter 35.

The shutters 3i and 35 are held in a normal position by the torsion springs 2| and 22 with the 'slots '38, 39, 4|, and 42 substantially perpendicular to, and out of alignment with, the slots 29 and 3! in the shield 25. In this position, 3, log 43, extending from the lower surface of the shutter, rides in the groove 32 adjacent the end Moi the groove 32. Similarly, shutter 35 has a lug 15 adapted to travel in groove 33 and bear against wall i at the end of the upper surface of theshield 25 by a retainer 47.

This retainer consists essentially of a pair of collars 8 and is, joined by central bar 5|. The collars i8 and 69 fit over-the shutters 34 and 35 and allow. access to the slots in the shutters. Each of the shutters is provided with a shoulder 52, against which the under surfaces of. the collars bear to hold the shuttersin place. It is generally desirable to provide legs 53 and 5 4 at the ends of the collars. These legs fit in grooves 55 and 56 in the shield 25, and 51 and 58 in the base member! adding to the rigidity of the outlet.

Apost .59 "extends downwardly from the center bar 5| of the retainer and .passes through opening 25 in the shield 25 into the cavity -|5 in the base member 5. Post 59 and cavity 15 are preferably non-circular in cross section and cooperates with legs 53 and 5 1450 align the parts of the outlet properly. Post 59 is "drilled and tapped for the reception of a screw 6|, illustrated in Figure 2, which holds the retainer firmly in place against the base member '5 of the outlet. In addition, the cover plate 'i, for the outlet is held in place by a screw 62, engaging threads in the post 59.

One of the important advantages of the outlet of the invention is the ease with which it may be assembled. The conductors |2 and I3 are readily slipped into position in the recesses '9 and II in the base member. Then torsion springs "2| and 22 are placed in the slots I6 and H with their lower ends extending into the grooves l8 and lil at the bottom of the sockets and the shield 25 is then rested on the base member with pin 30 extending into the hole 23. Shutters 3'4 and 35 are placed on the upper surfaceof the shield and held in placeby the retaine'r l'l. Arugged'imitary structure is provided by screw '61 engaging the base member 5 and the post 59 of the retainer 4?. In many instances, it will bedesirable that the bracket 3 be attached to the lower surface of the base -mlflbel 5 as the first step in the assembly.

All of the assembling operations may be easily and quickly performed. The parts slip easily into place and are held in place by gravity during the assembly. Springs l8 and I9 are in their normal uncompressed condition when inserted in sockets l6 and I1, thereby making it unnecessary to work against the force of the spring. After the outlet has been assembled, a finished appearance is provided by the installation of the cover plate I by means of the screw 62 engaging the post 59 of the retainer.

The electrical outlet herein described is used with electric appliances having their non-current carrying parts grounded. These appliances are generally equipped with a plug having an enlarged prong for connection with a ground Wire, and a small prong for connection with the live wire. The prongs of the plug are inserted in the slots 38 and 4| of shutter 34, the enlarged prong for connection with the ground being inserted in slot 38. Shutter 34 is rotated to bring the slots into alignment with the slots in the shield 25, directly below the shutter and the prongs of the plug are pushed through the slots in the shield into contact with the conductors I2 and I3.

The electrical outlet of this invention provides positive means for preventing accidental contact of a prong on a plug on an extension cord with the wrong electrical conductor. Since the shutter may move in only one direction, it is not possible to align the shortened slot 41 in the shutter 34 with the elongated slot 29 in the shield 25. Similarly, the enlarged prong of a, plu cannot be inserted in the elongated slot 29 0f the shutter and then brought into alignment with the shortened slot 3| in the shield 25. In this manner, danger of the grounded parts of the appliance being connected with the live wire in the receptacle is eliminated.

While this invention has been described in detail with respect to a particular modification of Number the invention, it is to be understood that the concept of this invention is not limited to those details, but is determined by the scope of the appended claim.

I claim:

An electrical outlet comprising a base member having a grounded conductor and a live conductor therein, a non-circular cavity in the base, a shield on the base covering the conductors and having a hole in register with the cavity in the base, a large slot in the shield in register with the grounded conductor, a small slot in the shield in register with the live conductor, a shutter pivotally mounted on the shield, said shutter having a large slot and a small slot therein, the slots in the shutter normally being out of register with the slots in the shield, a groove in the surface of the shield, a lug extending from the shutter into the groove, said lug and groove permitting rotation of the shutter only in a direction to align the large and small slots in the shutter with the large and small slots in the shield respectively, a retainer over the shutter holding the shutter against the shield, a post extending from the retainer into the cavity, and a screw engaging the post and the base to form a unitary structure.

PHILIP E. HAMILTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Ferris Aug. 27, 1929 Weiss July 11, 1933 Hamilton Apr. 11, 1939 FOREIGN PATENTS Country Date Germany Nov. 25, 1939 Number 

